Vacuum liners for defining a plasma in a high energy plasma device have been constructed using relatively thin wall sections made of stainless steel or Inconel. These sections offer high strength while forming a closed loop having sufficiently high electrical resistance that penetration times are acceptably low for magnetic fields generated by poloidal, toroidal or other associated magnetic systems for containing and energizing the plasma. Unfortunately, the thin sections, when used in a high energy plasma environment, may experience local surface melting upon plasma contact. The melting results in structural weakness and vacuum leaks in the liner.
In one attempt to prevent melting of the sections, short pieces of stainless steel rod limiters were installed on the inside surface of the sections. By absorbing the plasma energy, the rods protected the sections. However, contact with the plasma caused the plasma to deteriorate upon the introduction of metal impurities, which radiate and cause loss of power in the plasma. For further information regarding the structure and operation of such limiters, reference may be made to "Experimental and Computational Studies of Reversed-Field Pinch on TPE-IR(M)", by Ogawa et al. in "Proceedings of the 9th International Conference on Plasma Physics and Controlled Nuclear Fashion Research," Baltimore, 1982 (IAEA, Vienna, 1983), Vol. I, p. 575. Metallic limiters are also shown in U.S. Pat. No. 4,073,680.
In order to avoid the introduction of metal impurities into the plasma, carbon tiles have been used instead of the metal rods. However, the discrete tiles are not readily reliably fastened to the interior of the sections. In another attempt to protect the sections and avoid contamination of the plasma, rings of carbon tiles were placed at spaced locations in the vacuum chamber in the effort to make the plasma contact only the tiles. However, the expected reduction of the heat level on the sections was not found, and arcing occurred between the liner and the tiles which resulted in damage to the liner. For further information regarding such limiters, reference may be made to "Mushroom Limiter Studies in ZT-40M," Downing et al., Bull. Am. Phy. Soc., 27, 1108 (1982), and "Temperature and Resistivity of the ZT-40M RFP with Poloidal Limiters," Haberstich et al., Bull. Am. Phy. Soc., 28, 1097 (1983).
Mirror plasma apparatus has been proposed which utilizes shielding by arc discharge to form a blanket plasma and lithium walls to reduce neutron damage to a solid material wall which rotates to keep a liquid lithium layer against it. For further information regarding the structure and operation of this apparatus, reference may be made to U.S Pat. No. 4,260,455.